Allow alternate recovery

Include extract_elf_ramdisk to extract ramdisk from the FOTA
partition and check it to ensure that it is not a Sony FOTA
ramdisk. If it is a Sony FOTA ramdisk nothing changes, but if it
is not, then /sbin/ramdisk-recovery.cpio will be replaced by the
FOTA ramdisk allowing users to install an alternate recovery than
what is included in the boot image.

Change-Id: I6a570af905d15b0b4741ad04bc16f12fce00bb90